compress_pdf

#!/bin/bash -e
# Syntax:
#       compress_pdf [options] inFile [outFile]
#
#  Options:
#       See help
#       compress_pdf --help
#
# Requires:
#     gs
#
# History:
# Apr-2014  Yaswant Pradhan v1.0



usage(){
cat << EOF
NAME
    ${0##*/}, a gs wrapper to compress PDF files by controlling image
    resolutions of the original PDF.

SYNOPSIS
    ${0##*/} [OPTION] inFile [outFile]

DESCRIPTION
  Options:
    -h -? --help    show this message
    -d --dpi        image resolution required in the output pdf
    -s --size       desired output paper size (def: a4)
                    Paper sizes known to gs are available at
                    http://ghostscript.com/doc/current/Use.htm#Known_paper_sizes
    inFile          input pdf file
    outFile     optional  output filename base (def: inFile-{DPI}.pdf)

AUTHOR
       Written by Yaswant Pradhan.
EOF
}

# Check gs is avialable  on the system
which gs &> /dev/null
[[ $? -ne 0 ]] && echo -e "** ERROR: gs does not exist in path.\n" && exit 1

# -----------------------------------------------------------------------------
# Default settings:
# -----------------------------------------------------------------------------
DPI=300     # Default Image resolution
PAPER=a4    # Default Paper size

# -----------------------------------------------------------------------------
# Parse arguments:
# -----------------------------------------------------------------------------
while [[ $1 == -* ]]; do
  case $1 in
      -h|--help|-\?) usage; exit 0;;
      -d|--dpi) DPI=$2; shift 2;;
      -s|--size) PAPER=$2; shift 2;;
      --) shift; break;;
      -*) echo "invalid option: $1" 1>&2; usage; exit 1;;
  esac
done

if [[ $# -lt 1 ]]; then usage; exit 0; fi
inFile=$1   # Input File
[ ! -f "$inFile" ] && echo -e "** ERROR: '$inFile' does not exist.\n" && exit 1

outFile="${2:-$(basename $inFile .pdf)-${DPI}dpi.pdf}"
echo -e "Compressing to file: $outFile ... \c"

# -----------------------------------------------------------------------------
# Shrink PDF
# -----------------------------------------------------------------------------
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
   -dDownsampleColorImages=true \
   -dColorImageResolution="$DPI" \
   -dNOPAUSE -dQUIET -dBATCH -sPAPERSIZE="$PAPER" \
   -sOutputFile="$outFile" "$inFile"

st=$?
[[ "$st" -eq 0 ]] && echo -e "done." || exit "$st"